Late-onset mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome with mitochondrial DNA 3243A>G mutation masquerading as autoimmune encephalitis: A case report

Abstract

BACKGROUND

Here, we present a unique case of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome, which initially appeared to be autoimmune encephalitis and was ultimately confirmed as MELAS with the mitochondrial DNA 3243A>G mutation.

CASE SUMMARY

A 58-year-old female presented with acute-onset speech impediment and auditory hallucinations, symmetrical bitemporal lobe abnormalities, clinical and laboratory findings, and a lack of relevant prodromal history, which suggested diagnosis of autoimmune encephalitis. Further work-up, in conjunction with the patient’s medical history, family history, and lactate peak on brain lesions on magnetic resonance imaging, suggested a mitochondrial disorder. Mitochondrial genome analysis revealed the m.3243A>G variant in the MT-TL1 gene, which led to a diagnosis of MELAS syndrome.

CONCLUSION

This case underscores the importance of considering MELAS as a potential cause of autoimmune encephalitis even if patients are over 40 years of age, as the symptoms and signs are atypical for MELAS syndrome.

Keywords: MELAS; Mitochondrial DNA mutation; Encephalitis; Case report

Core Tip: Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome is a multimitochondrial disease caused by DNA mutations and respiratory chain defects that is frequently misdiagnosed. Here, we describe a 58-year-old patient with MELAS syndrome who initially presented with acute cognitive impairment, tinnitus, and headache and was subsequently misdiagnosed with autoimmune encephalitis. The final diagnosis was based on MELAS mutation blood tests and magnetic resonance imaging results. The patient was treated with appropriate medication and gradually improved. This case shows that MELAS syndrome should be diagnosed only after other causes, including autoimmune encephalitis, have been ruled out and the atypical clinical features of MELAS syndrome, such as older age of onset, have been considered.